The field of invention is optical communications, particularly wavelength division multiplexing.
Optical communications is a fast-growing field. An optical communication system refers to any system that uses optical signals to convey information over an optical waveguiding medium. Optical communication systems can be employed in telecommunications, cable television, local area networks, etc.
It has been found that the usable transmission capacity of a given optical transmission medium can be substantially increased by use of wavelength division multiplexing, or WDM. With WDM, two or more channels are provided over a common optical waveguide, the channels being differentiated by optical wavelength. Signal transmission is distributed to designated locations via routers or switches.
While it is well known in the art to transmit the local router or switch output as an optical signal, that signal is not compatible with the optical signal used in the WDM equipment. Thus, at the point of interface with the WDM system, the optical signal from the originating switch/router is converted into an electrical signal, which is converted in turn into another optical signal compatible with the WDM system in order to be transmitted over the WDM portion of the transmission path, such as a Wide Area Network (WAN).
Systems use optical-electrical-optical conversion at the WDM interface because the characteristics of the optical signal generated by the sources currently used in the art, such as spectrum, power, etc., are incompatible with the signals used in the WDM equipment. These conversion steps are cumbersome and resource-consuming. For larger data transmission systems, resources (such as modulation devices or router/switch interfaces) required to perform opto-electrical conversion are prohibitively costly. Therefore, there is a need for a more efficient optical system that performs the same function of data transmission without requiring unduly cumbersome opto-electrical conversion steps, while using substantially less interface connections on the routers/switches.
It is desirable to avoid the optical-electrical-optical conversion of the present WDM systems, an objective realized according to the invention by causing the output signal from the router to be in an optical form compatible with the WDM equipment. This will result in two advantages: direct compatibility with modem WDM transmission systems in the WAN, and optical switching in the LAN (Local Area Network) and MAN (Metropolitan Area Network). In order to accomplish this, the network address/subnet for an originating signal is mapped at the router output directly to the optical channel for that address in the WDM system. To this end, the originating switches and/or routers are equipped with multi-frequency laser arrays and multi-channel receivers. The same implementation can also be applied for the originating network or host. For implementation in a WDM environment, network addresses are mapped to different wavelengths. The method of the invention maps a network address/sub-network directly from a source/originating network to a channel of a multi-channel optical transmission medium (typically a WDM optical system) thereby effecting integration of the optical channel in the originating routers and switches.
The invention advantageously removes unnecessary, expensive opto-electric conversion procedures at the WDM interface by directly mapping the network address/subnet to the WDM wavelength associated with that address/subnet at a local network, router or switch. Another embodiment of the invention maps the network address/subnet to the WDM wavelength directly at the information source, i.e., routers/switches and ultimately the hosts (computers) where the data originate. In addition to elimination of unnecessary, cumbersome opto-electrical conversion steps, the invention greatly reduces the number of Optical/electrical interfaces needed to interconnect a large number of routers and switches over local or wide area networks by integrating WDM address mapping functions onto the local network routers/switches or the information source directly.